The 'fire fairy' you pick up to deal with logs is something different, I think it was renamed to 'fire fae' in later versions.

Now, the four fairies you need to pick up, all of whom are in pink grass:

- Blu or Milli: The water one, at Darkshawl Peak.
- Leea: First found in Gad'riel Mountain's small pink grass patch around a small tree, but if I remember you can find Bound ones in Wicked Woods.
- Embud or Embellia: First found in the pink grass south of Xelos City around the tower, but can also be found in Darkshawl Peak at a higher level.
- Gloombud or Noxy: First found in the pink grass inside the twon of Gad'riel Peak, but Noxy can be found in the main story's final area.

If it still doesn't work, level all of them up to 40 to get their final forms: Millian, Sindela, Kthuune, and Duskalina respectively. (Duskalina isn't the final form for that last one, but it's the one depicted in the achievement.)

This should do it for you.

Can you help me where to find the last gems for the portal of the post game (mega city?) Only have the fairy and fire one and cant find a guide about it